[from Heisenberg's Uncertainty Principle in quantum physics] A bug
that disappears or alters its behavior when one attempts to probe or
isolate it. (This usage is not even particularly fanciful; the use of a
debugger sometimes alters a program's operating environment significantly
enough that buggy code, such as that which relies on the values of
uninitialized memory, behaves quite differently.) Antonym of
Bohr bug; see also mandelbug,
schroedinbug. In C, nine out of ten heisenbugs
result from uninitialized auto variables,
fandango on core phenomena (esp. lossage related to corruption of the
malloc arena) or errors that
smash the stack.